1. Field of the Invention
The present invention relates to an optical recording medium. More particularly, the present invention relates to a dye for an optical recording medium.
2. Description of Related Art
Compact disk (CD) comprises the following advantageous qualities: high storage capacity, small volume, stability over long storage period, low production cost, high compatibility and low error rate. Compact disk thus becomes a major optical information recording medium. Amongst the various types of compact disk, the most popular is the Compact Disk-Recordable (CD-R), which is a recording medium capable of recording and retrieving information by means of a laser beam having a wavelength of 770 nm to 830 nm.
Through the popularization of multimedia, large amount of textual, sound and image data are generated. The original 650 MB capacity CD-R can no longer accommodate the audio-visual demand of the next generation. Therefore, the industry introduces a Digital Versatile Disc-Recordable (DVD-R) with a memory capacity several times of that of the CD-R. The Digital Versatile Disc-Recordable (DVD-R) has the capability for recording and retrieving information in a high density because semiconductor lasers having shorter wavelengths than that for the conventional CD-R (for example, lasers having wavelengths 620 nm to 690 nm) are used for recording and retrieving information. DVD-R is going to be a major optical information recording medium.
The write-once version of the DVD-R uses an organic dye as a recording layer. Recording is performed by irradiating a short-wavelength laser to the dye-based recording layer. Upon the absorption of the laser beam energy, the irradiated portion of the recording layer will undergo a thermal deformation. This basically forms a pit that represents the digital bit being recorded. The most commonly used organic dye includes cyanine dye, azo dye, benzofuryl ketone dye, indigo dye, etc. However, using the above dyes as a recording layer for an optical recording medium, there is a problem of poor optical stability. Especially the short wavelength laser is used to perform the recording/reproduction, the stability of the stored data, the reflection rate and photosensitivity will be adversely affected. Normally, the above dyes are incorporated with the various organic dye metal chelate compound to improve the photo stability.
A conventional optical recording medium dye, as disclosed in U.S. Pat. No. 5,330,542, includes an azo metal chelate compound comprising an azo type compound of the following structure (I): 
wherein, x is a group having an active hydrogen; A is a residue forming a benzene ring derivative, for example, benzene, naphthalene, etc., together with two carbon atoms; and B is a residue forming a benzene ring derivative or a heterocyclic ring derivative, for example, benzene, naphthalene, thiazole, benzothiazole, pyridine, quinoline, pyridobenzothizole, pyrazole, etc., together with a carbon atom and a nitrogen atom.
Another conventional optical recording medium dye, as disclosed in U.S. Pat. No. 6,225,023, includes an azo metal chelate compound comprising an azo type compound of the following structure (II) or (III): 
or
wherein each of A1 and A2 is a residue forming a benzene ring derivative or a heterocyclic ring derivative together with two carbon atoms. The heterocyclic ring derivative includes, for example, benzene, naphthalene, pyridine, etc.; each of B1 and B2 is a residue forming together with the carbon atom and the nitrogen atom to form a heterocyclic ring derivative, for example, benzene, naphthalene, thiazole, benzothiazole, pyridine, quinoline, pyridobenzothizole, pyrazole ring, etc.; Y is a C1-6 linear or branched alkyl group.
The above azo type of dye is formed by having the nitrogen on the heterocyclic ring and the active group on the benzene ring to chelate with the metal. It is therefore necessary to introduce an active group to the benzene ring. An introduction of an active group to the azo compound normally requires other coupling processes.
Accordingly, the present invention provides an optical recording medium dye. The dye of the present invention is an azo metal chelate compound, wherein the nitrogen atom on the heterocyclic ring of the azo compound directly chelates with the metal. An introduction of an active group is precluded.
The present invention further provides an optical recording medium dye wherein the optical stability of this material is favorable. Further, the material is applicable as a data layer of an optical recording medium in which short wavelength laser can use for recording or reproduction.
In accordance to the present invention, an optical recording medium dye is provided, wherein this optical recording medium dye is an azo metal chelate compound. This azo metal chelate compound comprises an azo type compound of the following structure (IV): 
wherein A3 and B3 are residues forming a heterocyclic ring derivative together with the carbon atom and the nitrogen atom. The heterocyclic ring derivative includes derivatives of an imidazole group, a thiazole group, an oxazole group, a benzothiazole group, a benzopyridoxinethiazol group, a pyridoxinethiazole group, a pyridine group, a pyridazine group, a pyrimidine group, a pyrazine group, a triazine group, a quionline group, a pyridobenzothiazole group, a pyrazole group, or the above heterocyclic ring derivatives that contain the following substituent: a halogen atom, a nitro group, a cyano group, an amino group, a formyl group, a hydroxyl group, a carboxyl group, an alkylamino group, a substituted C1-15 straight chain alkyl group, an unsubstituted C1-15 straight chain alkyl group, a branched alkyl group, a cycloalkyl group, an alkoxy group, an alkyl carbonyl group, a straight chain alkenyl group, a branched alkenyl group, a cylcoalkenyl group, a hydroxyalkyl group, an alkoxycarbonyl group, an alkoxycarbonylallyl group, an alkylthio group, an alkylsulfonyl group, an aryl group or a heterocyclic group.
If the 
part of the above structure (IV) is, for example,
a pyridine derivative, the above azo compound structure (V) can be represented as follow: 
wherein R1 is, for example, a hydrogen atom, a C1-6 straight chain or branched alkyl group, an amino group, an alkylamino group or a tolylamino group; R2 is, for example, a hydrogen atom, a hydroxyl group, a halogen group, an ether group, an ester group or a C1-6 straight chain or branched alkyl group; R3 is a hydrogen atom, a C1-6 straight chain or branched alkyl group; R4 is, for example, a hydrogen atom, a C1-6 straight chain or branched alkyl group or a halogen atom; A3 is a residue forming a heterocyclic ring derivative together with the carbon atom and the nitrogen atom.
The above heterocyclic ring derivative includes derivatives of an imidazole group, pyrazole group, a triazole group, a tetrazole group, a benzoimidazole group, a thiazole group, an isothiazole group, a thiadiazole group, a thiatriazole group, a benzothiazole group, an oxazole group, an isoxazole group, an oxadiazole group, an oxatriazole group, a benzoxazole group, etc.
Thus, the 
part of the above structure (V) includes, for example, 
wherein the substituent E1 to E38 each includes, for example, a hydrogen atom, a halogen atom, a nitro group, a cyano group, an amino group, a formyl group, a hydroxyl group, a carboxyl group, an alkylamino group, a substituted or unsubstituted C1-15 straight chain alkyl group, a branched alkyl group, a cycloalkyl group, an alkoxy group, an alkyl carbonyl group, a straight chain alkenyl group, a branched alkenyl group, a cycloalkenyl group, a hydroxyalkyl group, an alkoxycarbonyl group, an alkoxycarbonylallyl group, an alkylthio group, an alkylsulfonyl group, an aryl group or a heterocyclic group.
The metal ion for forming the azo metal chelate compound includes nickel, cobalt, iron, ruthenium, rhodium, palladium, copper, iridium, platinum, zinc, etc.
The optical recording medium dye of the present invention is an azo dye of a heterocyclic ring and a heterocyclic ring. Further, chelating with the metal is through the nitrogen on the heterocyclic ring. Introduction of an active group is thus obviated. Further, the greatest UV-V is absorption wavelength is lower than 650 nm. The azo recording medium dye of the present invention is thus applicable as a recording layer of an optical recording medium in which short wavelength laser can use for recording and reproduction.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
The following embodiment details the optical recording medium dye of the present invention.
The present invention provides an optical recording medium dye, which comprises an azo type dye metal chelate compound that comprises a heterocyclic ring and a heterocyclic ring. This type of azo metal chelate compound has the following structure (IV): 
wherein A3 and B3 are residues forming a heterocyclic ring derivative together with the carbon atom and the nitrogen atom, and the heterocyclic ring includes derivatives of an imidazole group, a thiazole group, an oxazole group, a benzothiazole group, a benzopyridoxinethiazole group, a pyridoxinethiazole group, a pyridine group, a pyridazine group, a pyrimidine group, a pyrazine group, a triazine group, a quinoline group, a pyridobenzothiazole group, a pyrazole group, or the above heterocyclic ring derivatives that contain the following substituent: a halogen atom, a nitro group, a cyano group, an amino group, a formyl group, a hydroxyl group, a carboxyl group, an alkylamino group, a substituted C1-15 straight chain alkyl group, an unsubstituted C1-15 straight chain alkyl group, a branched alkyl group, a cycloalkyl group, an alkoxy group, an alkyl carbonyl group, a straight chain alkenyl group, a branched alkenyl group, a cylcoalkenyl group, a hydroxyalkyl group, an alkoxycarbonyl group, an alkoxycarbonylallyl group, an alkylthio group, an alkylsulfonyl group, an aryl group or a heterocyclic group.
If the 
part of the above structure (IV) is, for example, a pyridine derivative, the above azo compound structure (V) can be represented as follow: 
wherein R1 is a hydrogen atom, a C1-6 straight chain or branched alkyl group, an amino group, an alkylamino group or a tolylamino group; R2 is a hydrogen atom, a hydroxyl group, a halogen atom, an ether group, an ester group or a C1-6 straight chain or branched alkyl group; R3 is a hydrogen atom, a C1-6 straight chain or branched alkyl group; R4 is a hydrogen atom, a C1-6 straight chain or branched alkyl group or a halogen atom; A3 is a residue forming a heterocyclic ring derivative, for example, derivatives of an imidazole group, a pyrazole group, a triazole group, a tetrazole group, a benzoimidazole group, a thiazole group, an isothiazole group, a thiadiazole group, a thiatriazole group, a benzothiazole group, an oxazole group, an isoxazole group, an oxadiazole group, an oxatriazole group, a benzoxazole group, etc., together with the carbon atom and the nitrogen atom.
Thus, the 
part of the above structure (V) includes, for example, 
wherein the substituent E1 to E38 each includes, for example, a hydrogen atom, a halogen atom, a nitro group, a cyano group, an amino group, a formyl group, a hydroxyl group, carboxyl group, an alkylamino group, a substituted or unsubstituted C1-15 straight chain alkyl group, a branched alkyl group, a cycloalkyl group, an alkoxy group, a carbonyl group, a straight chain alkenyl group, a branched alkenyl group, a cycloalkenyl group, a hydroxyalkyl group, an alkoxycarbonyl group, an alkoxycarbonylallyl group, an alkylthio group, an alkylsulfonyl group, an aryl group or a heterocyclic group.
The halogen atom includes fluorine, chlorine and bromine. The alkyl group includes, for example, methyl, ethyl, propyl, isopropyl, butyl, pentyl, etc. The cycloalkyl group includes cyclopropyl, cyclobutyl, cyclopentyl, etc. The alkoxy group includes methoxy, ethoxyl, n-propoxyl, isopropoxyl, n-butoxyl, i-butoxyl, t-butoxyl, pentoxyl, etc. The alkyl carbonyl group includes formyl, acetyl, propionyl, butyryl, i-butyryl, etc. The alkenyl group includes vinyl, propenyl, butenyl, pentenyl, hexenyl, etc. The cycloalkenyl group includes cyclopentenyl, cyclohexenyl, etc. The hydroxyalkyl group includes, for example, hydroxymethyl, hydrozyethyl, etc. The alkoxycarbonyl group includes, for example, methoxycarbonyl, ethoxycarbonyl, n-propoxycarbonyl, iso-propoxycarbonyl, n-butoxycarbonyl, iso-butoxycarbonyl, tert-butoxycarbonyl, etc. The alkylamino group includes, for example, methylamino, ethylamino, n-propylamino, n-butylamino, dimethylamino, diethylamino, etc. The alkoxycarbonylallyl group includes, for example, methoxycarbonylmethyl, ethoxycarbonylmethyl, n-propoxycarbonylmethyl, iso-propoxycarbonylmethyl, etc. The alkylthio group includes, for example, methylthio, ethylthio, n-propylthio, iso-butylthio, tert-butylthio, etc. The alkylsulfonyl group includes, for example, methylsulfonyl, ethylsulfonyl, n-propylsulfonyl, iso-propylsulfonyl, n-butylsulfonyl, iso-butylsulfonyl, tert-butylsulfonyl, etc. The aryl group includes, for example, phenyl, tolyl, xylyl, ethylphenyl, etc. The hetercyclic group includes pyridyl, imidazolyl, furyl or thenoyl, etc.
Further, the metal ion that forms the chelate compound with the azo dye compound of the present invention includes, for example, nickel, cobalt, iron, ruthenium, rhodium, palladium, copper, iridium, platinum, zinc, etc.
The method for fabricating an optical recording medium dye of the present invention comprises subjecting the heterocyclic ring derivative (such as, derivatives of imidazole, pyrazole, triazole, tetrazole, benzoimidazole, thiazole, isothiazole, thiadiazole, thiatriazole) to heavy nitridation, followed by performing a coupling reaction with pyridine A chelating reaction with metal ion is further performed. The heterocyclic derivative is first dissolved in acetic acid. Concentrated sulfuric acid is drop added to the heterocyclic derivative solution, followed by adding nitrosylsulfuric acid. The mixture is then allowed to react for three hours at low temperature, followed by adding urea to obtain solution (A). The pyridine derivative is dissolved in water or alcohol type of solvent, followed by adding sodium acetate. The above solution (A) is further dropped added to the pyridine solution. After the entire solution (A) is added, mixing is continued for another three hours. Filtering is then performed to collect a solid substance, wherein the solid substance constitutes an azo product. The above azo product is dissolved in an alcohol type of solvent. Nickel acetate is drop added to the azo product solution. After mixing for 6 hours, a solid substance is collected subsequent to filtering. The solid substance constitutes an azo metal chelate compound.
The above heterocyclic ring derivative includes derivatives of an imidazole group, pyrazole group, a triazole group, a tetrazole group, a benzoimidazole group, a thiazole group, an isothiazole group, a thiadiazole group, a thiatriazole group, a benzothiazole group, etc., for example, 2-aminoimidazole, 2-amino-4,5-dicyanoimidazole, 3-aminopyrazole, 2-aminotrizole 3-amino-1,2,4-triazole, 3-amino-5-methylthio-1H-1-2-4-triazole, 5-amino-1,2,3,4-tetrazole, 4-amino-1,2,3,5-tetrazole, 2-aminobenzoimidazole, 2-aminothiazole, 3-aminoisothiazole, 3-amino-t-methylisothiazole, 2-amino-5-methyl-1,2,4-thiaziazole, 5-amino-1,2,3,4-thiatrizole, 4-amino-1,2,3,5-thiatriazole, 2-aminobenzothiazole, 2-aminoxazole, 3-aminoisoxazole, 3-amino-5-methylisoxazole, 2-amino-5-methyl-1,2,4-oxadiazole, 5-amino-1,2,3,4-oxatriazole-4-amino-1,2,3,5-oxatriazole, 2-aminobenzoxazole, etc.
The above pyridine derivative includes, for example, 2-amino-3-hydroxypyridine, 2-bromo-3-hydroxypyridine, 3,5-dibromopyridine, 3-chloropyridine, 3,5-dichloropyridine, 3-bromopyridine, 3,5-dibromopyridine, etc.